Transformer for amplifier devices



Feb. 12, 1929. 1,102,012

F. CARBENAX TRANSFORMER FOR AMPLIFIER DEVICES Original Fil'ed May 17. 1923 INVENTOR' FERNMD cnaaum I a I ORNEY.

Patented F ch. 12, 192 9.

UNITED SITAT rnnnanncnmannar, or rants, Flam.

TnANsronmEn-ron AMPLIFIER nnvrons.

Application filed May 17, 1323, Serial No. 639,701, and in France June 1,1922. Renewed August 3, 1928.

The presentfinvention relates 'to a novel method ofbuil'dingtransformers of the kind used invcombination. with high frequency .currentamplifiers. V I

Transformers are already. known of the ferro-magnet-ic core type which servefori'n suring connection between the grid or the plate circuit of a threeelectrode tube, and the external circuit (plate or grid circuit of the three-electrode tube of the neighbor ing stage, or input or output circuit of the amplifier tube). In the construction of these transformers, one chief aim is to eliminatethe capacity between theprimary and the secondary windings, and with this end inview it has been the general practice to keep these windings spaced from each other by arrangingeach winding upon a cardboard cylinder placed upon the core, the two cylinders being i of widely differing diameter in order to leave several millimeters clearance-space between the two" windings.

It is an object of this invention to produce a transformer of the type described having an appreciable capacity between its windings. It is another object to produce such a transformer which may be relatively simply and economically constructed. Still another object of the invention is toproduce a transformer which shall operate efliciently over a wide range of wave lengths. Still other'objects of the invention will be apparent from the specification which should-be read in connection with the accompanying drawing in which:

Fig. 1 is a sectional view of a transformer constructed according to my invention, and Fig. 2 is across section on line 2'2 of Fig. 1.

Now, contradistinct from the prior practice, according to the present invention, an

' appreciable capacity is provided between the windings; for instance, one winds the two coils upon one another, each of them being" preferablyrestricted to one layer (pile-winding) with the interposition, if necessary, of a sheet of paper or other insulating material of very great thinness. In this manner, the

capacity between the windings is increased, and the result thereof is that the limits or range of frequencies for which the amplifier can be usefully employed, are enlarged in a very economical manner. The device when so constructed constitutes at the same time an inductive and capacitive coupling and the sum of the effects, which vary withwave length changes in inverse sense, preserves a convenient value betweenthe wide wavelength limits. At the higher range of frequencies for which the transformer is designed to he used as a coupling thecapacitative features of the coupling predominate and at the lower frequencies the inductive features of the coupling predominate. At the ntermediate frequencies the capacitative and inductive features coact in different degrees, the relation between the two being of course determined by the particular frequency. It

in the same sense, the end of the primary connected with the plate of a triode must be upon the same side of the winding as the end of the secondary connected with the *grid of the triode next following.

Referring now to the accompanying drawing 1 represents a hollow cylindrical casing, preferably of non-magnetic insulating material,,closed at one end. The open end of the casing is close by the cover 6 which may be of the same material as the casing itself.

An iron core 5, shown as consisting of a bundle of iron wires, is supported axially of the casing in grooves 7 and 8 in the closed end and cover of the casing, respectively. It will be noted that a considerable air space is left between the iron core and the cylindrical walls of the casing.

On the outside ofthe cylindrical casing are wound the transformer coils 2 and 3 separated from each other by a thin sheet of insulating material 4, which may very well be a sheet of paper, the thickness being exaggerated in the drawing to make the illustration clear. These coils are mountedabout midway of the ends of the casing and are shown as covering only a small portion of the area. It is to be understood that the form, constitutiom a'nd dimensions of the magnetic core are arbitrary, as are likewise the constants of the windings (number of turns, cross-sectional area of the wire, etc), and

these factors be varied in cbnforlnity with the-purpose or service for which the device shall be used, and the effects that shall be produced. One of the most preferable plans of building the core should be to make "it of a bundle of very thin iron wires, conveniently annealed and possessing "igh permeability,

andthus constituting a core of straight form It should be noted that various arrangements of windings. adapted to, obtain sufiicient capacity between theriinary and secondary windings may be utiviz ejd without departing from the spirit and ideaunderlying the pres ent invention. F or instance, the primary and secondary windings can be wound simultaneously two wires in hand' in a way so as to placetheir respective spires contiguous, etc.

Having described my invention, what I claim is 1. A radio frequency coupling transformer comprising primary and, secondary windings, one directly superposedon the other for increasing the capacity therebetween, amagnetic core consisting of a bundle of fine iron wires of high permeability disposed centrally of the windings and spaced therefrom, said transformer windings being thereby adapted to progressively change the character of the coupling from inductive to capacitive as the frequency changes from a lower to a higher frequency within the operating range.

2/ A high frequency transformer comprising primary and secondary windings, each consisting of a single layer and directly superposed one on the other for increasing the capacity therebtween, and a magnetic core composed of a bundle of Very fine ironwires possessing high permeability disposed centrally of the windings and spaced therefrom.

3. An arrangement for inductively and capacitively coupling a pair of high frequency current amplifiers, comprising a cen trally arranged magnetic core of very fine iron wires high permeability, a primary winding arranged to. be connected to the output of one of'said amplifiers disposed around said core and spaced therefron'i, a secondary winding arranged to be connected to the. input of the second of said amplifiers superposed on said primary; and a thin sheet of insulation disposed between both windings, whereby the character of the coupling is changed from inductive to capacitive as the frequency changes from a lower to a higher value within theloperating ran -e.

FERNAND GARBENK 

